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ABSTRACT Forces on bends and T-joints have been measured in a one inch diameter horizontal air-water setup for all flow regimes. The highest force levels are observed in the slug flow regime, whereas annular flow gives the lowest force levels. The amplitude was measured to be between 1 and 10 times the liquid momentum based on the mixture velocity. The results for a real T-joint were significantly lower than for the bends. In case of slug flow, the measurements can be modelled assuming a simple slug unit model. For the annular and stratified flow, a mixture model is the most appropriate.
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
ABSTRACT Long liquid slugs reaching several hundreds pipe diameter may appear when transporting gas and liquid in horizontal and near horizontal pipes. The long slugs cause system vibration and separation difficulties that may lead to operational problems. Although mainly short hydrodynamic slugs have been observed in offshore production fields, the appearance of the long slugs becomes more likely as the fields become older, giving reduced production rates and a reduced operational pressure. In this paper we present a method for reducing the negative effects of the long slugs in horizontal pipes. The method is based on increasing the slug frequency, at constant flow conditions, by using an upwardly inclined inlet section. The flow in the inclined section results in a faster formation of slugs upstream in the pipeline. As a result, the slug frequency increases and slugs become fully developed earlier in the pipe preventing further growth into the long slug region. For validation of the method, experiments have been carried out in a 137 m long air-water horizontal pipe flow with an internal diameter of 0.052 m, using different inlet sections. The results show that, at relatively large flow rates, there is an inverse relationship between the slug length and frequency. However, the slug length becomes less sensitive to the change in slug frequency at low flow rates.
ABSTRACT A subsea field in the deepwater of the Gulf of Mexico will be installed and commissioned in phases. The uniqueness of the subsea construction activities presented several flowline displacement operational challenges with oil circulation and seawater circulation procedures that will be conducted from the host platform. In order to validate and optimize the operational procedures for these displacement operations, transient simulations have been performed. Of particular concern is the effectiveness of the dead oil sweep of live fluid. Preliminary simulations using the standard version of a three-phase transient simulator indicate that available dead oil circulation rates are insufficient to sweep remnant gas from downwardly inclined sections of the flowline, thereby generating an ongoing hydrate formation hazard. In order to evaluate the effectiveness of solution of this remnant gas in the highly undersaturated dead oil, the Compositional Tracking version of the simulator was employed. Compositional Tracking simulations indicated that the remnant gas is promptly removed by solution in the dead oil. The comparison between the standard and Compositional Tracking simulations illustrates another class of operations in which accounting for the transient variation in fluid chemical composition is important.
- North America > United States (0.71)
- North America > Mexico (0.61)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (1.00)
- Facilities Design, Construction and Operation > Flow Assurance > Hydrates (0.88)
ABSTRACT There are many sources of uncertainty in multiphase fluid flow models. However, most models are deterministic. One of the sources of uncertainty is closure relationships. In this paper, we present a wrap-around uncertainty propagation tool designed to study and quantify the impact of closure relationship uncertainties on multiphase flow model predictions. As a case study, we examined the impact of slug length uncertainty on pressure drop and liquid holdup predictions of Tulsa University Fluid Flow Projects (TUFFP) Unified Model(1) for two-phase vertical flows. The results suggest that a ± 50% slug length uncertainty can result up to 40% uncertainty in pressure drop predictions for some operating conditions, and almost no uncertainty for others.
- Research Report > New Finding (0.67)
- Research Report > Experimental Study (0.49)
ABSTRACT To design and evaluate slugging control strategies, a simulator that is capable to simulate severe slugging accurately with limited CPU-needs is required; therefore a drift flux simulator was developed. The drift-flux simulator was used to simulate a field case. The pressure drop was predicted very well. However, an additional horizontal length was needed in the simulations to obtain slugging. This additional requirement is in-line with known shortcomings of multiphase models identified in literature. Aside this criterion, also a minimum hydraulic jump was required. The current drift-flux simulator is suitable for case specific control strategy development and testing.
- Well Drilling > Drilling Operations (1.00)
- Well Completion (1.00)
- Reservoir Description and Dynamics (1.00)
- (3 more...)
To avoid or minimise the adverse impact of such instability, operating conditions should be selected properly and appropriate slug mitigation techniques should be adopted. An efficient model for predicting multiphase flow behaviour in pipeline-riser system is highly desirable to provide essential information for the design and operation of production system. Various severe slugging related models have been proposed by many researchers since the phenomenon was identified by Yocum (1). In terms of the application of these models they can be classified into three categories: (a) predicting the conditions under which severe slugging occurs (or the stability boundary between severe slugging and non severe slugging region in the flow regime map) (2-4); (b) predicting the key characteristic parameters of severe slugging such as slug frequency, slug length, slug velocity, riser base/top pressure, liquid buildup time, slug production time, etc. (5-10); (c) predicting the flow behaviour in pipeline-riser systems operated with slug mitigation techniques such as increasing backpressure, choking, gas lift, etc. (11-13). Models (a) are mainly steady-state models while Model (b) and (c) are transient models because the characteristics of severe slugging are time and space dependent.
- North America (0.28)
- Europe (0.28)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Risers (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Pipeline transient behavior (1.00)
ABSTRACT Hydrodynamic slug flow is the prevailing flow regime in oil production, yet industry still lacks a comprehensive model, based on first principles, which fully describes slug flow. This paper describes a graphical technique out of which - given the superficial gas and liquid velocities - the overall hold-up, hold-up in the slug body, and hold-up in the bubble region between slugs can be determined. The model is compared to experimental slug data as well as against other empirical methods. BHR Group 2010 Multiphase 7 345 1 INTRODUCTION Theoretical prediction of the onset of hydrodynamic slug flow has received considerable attention in the literature. For example, hydrodynamic slug flow should become more prevalent as the gas density increases, due to increased Bernoulli lifting forces on the perturbed interface.
ABSTRACT Separation of fine particulate matter from complex slurry mixtures is a challenge for mineral and hydrocarbon extraction, environmental cleanup, and drilling engineering. A dedicated and fully equipped experimental rig was utilized at the University of Alberta, Edmonton to observe and correlate the frequency and magnitude of coherent turbulent flow structures and to quantify the selective radial transport (grading) of particles from the moving bed onto the main turbulent flow. A preferential removal of coarser particles (from a bed containing fractions from 0.1–100 μm of glass beads).controlled by bursts-sweep near-wall activity, is observed and results are satisfactorily compared with a dedicated mechanistic model discussed in this paper. Experimental and numerical results presented demonstrate the salient effect of near-wall interface burst activity driven by turbulent flow on the selective removal-deposition transport of fines during bed transportation of slurries.
- North America > Canada > Alberta (0.54)
- North America > United States (0.46)
- Reservoir Description and Dynamics (1.00)
- Facilities Design, Construction and Operation (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.66)
ABSTRACT By the nature of their design and because of the lack of residence time, separation efficiency of compact separators is inferior to the bulky gravity separators. Irrespective of this, compact separators have found many applications where complete separation is not necessary. This paper reports on an experimental study of a novel axial flow cyclonic separator (I-SEP) in air water two phase flows. The experimental matrix covered slug and annular flow regimes, with inlet gas volume fractions between 35% to 98%, and the mixture velocity at inlet to the separator ranging from 5m/s to 60m/s. As direct measurements of gas and liquid flow rates at the I-SEP outlets were not possible, in these experiments, the outlets of the I-SEP were connected to downstream gravity separators. The gas and liquid flows at the I-SEP outlets were inferred by measuring the ‘pure’ gas and liquid flow rates at the outlets of the gravity separators. As the two-phase flow is highly pulsating and changing instantaneously, Kalman filter technique was used and was found to be more accurate than using simple mass balance method. The performance parameters, i.e. the Gas Carry-Under (GCU) and the Liquid Carry-Over (LCO) were found to be highly non-linear. An artificial neural network was constructed to predict the separation efficiency for given flow conditions. It was found that by manipulating the pressure difference between the two outlets and the inlet, the GCU and LCO could be controlled. The inverse function of the neural network was used to predict the required pressure differences for the given inlet conditions and the required separation efficiency. This approach will assist the operator to manually or automatically control of the I-SEP performance.
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Facilities Design, Construction and Operation > Processing Systems and Design > Separation and treating (1.00)
- Data Science & Engineering Analytics > Information Management and Systems > Neural networks (1.00)
ABSTRACT Data from two and three phase high pressure experiments using North Sea crude oil, brine and hydrocarbon gas were compared with results from the OLGA point model in the stratified, intermittent and dispersed flow regimes. Two water cuts were investigated for the three phase experiments. Experimental flow regimes were determined using time series from a traversable gamma densitometer. Phase holdups were determined using either the traversable gamma densitometer or the stationary gamma densitometer. Pressure drops were measured using pressure transducers.
- Europe > United Kingdom > North Sea (0.25)
- Europe > Norway > North Sea (0.25)
- Europe > North Sea (0.25)
- (2 more...)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)